Among all-solid-state batteries, thin film lithium batteries have been researched and developed primarily as a small battery having a very small capacity of several to several tens of microampere-hours. The structure is a laminate structure in which, for example, a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are sequentially formed on a metal foil or a metal thin film formed on a ceramic substrate made of alumina or the like, which is used as a collector. As methods for forming the layers mentioned above, for example, a vapor phase deposition method, such as a sputtering method, is used, and an oxide and a Li metal are used for the solid electrolyte layer and the negative electrode layer, respectively (for example, see Patent Documents 1 to 5 and Non-Patent Documents 1 and 2).
In addition, in order to increase the capacity, an all-solid-state lithium secondary battery using a powdered solid electrolyte has been investigated. This battery generally has a laminate structure in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are sequentially laminated to each other. As a positive electrode, a mixture composed of a powdered solid electrolyte, a powdered positive electrode active material, and a powdered conduction assistant primarily formed of carbon has been used, and as a negative electrode, besides a Li metal foil, a metal, such as Al or In, forming an alloy with Li has been used. As a solid electrolyte, a sulfide-based material having relatively high ion conductivity has been used in many cases. Since using no organic electrolyte solution, the all-solid-state batteries are superior in safety and, in addition, are very stable and not degraded at a high temperature region of 100° C. or more (for example, see Patent Documents 6 to 8).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-235155
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-179158
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2004-127743
Patent Document 4: Japanese Unexamined Patent Application Publication No. 10-83838
Patent Document 5: Japanese Unexamined Patent Application Publication No. 4-231346
Patent Document 6: Japanese Unexamined Patent Application Publication No. 2004-95243
Patent Document 7: Japanese Unexamined Patent Application Publication No. 2003-68361
Patent Document 8: Japanese Examined Patent Application Publication No. 6-54687
Non-Patent Document 1: Electrochemistry Communication 6, (2004), pp. 417-421
Non-Patent Document 2: Solid State Ionics 69, (1994), pp. 357-368